I. Technical Field
This disclosure relates generally to systems, apparatus and methods for communicating assistance information using non-carrier or third party servers, and more particularly to locating base stations and mobile devices using Observed Time Difference of Arrival (OTDOA) assistance data.
II. Background
Users of mobile devices and network operators often desire to know where a mobile device is located. Although, mobile devices sometimes include a global positioning satellite (GPS) system or other global navigation satellite system (GNSS) to estimate a position, many mobile devices do not contain satellite navigation hardware. In other instances, the inadequate availability of satellite signals at a location or prolonged satellite signal acquisition and capture durations may limit location determination. In some of these cases, a carrier may provide assistance data to speed acquisition of satellite signals and/or provide information about terrestrial signals from base stations, access points, micro-cells, pico-cells, femto-cells and other terrestrial transmitters. Some networks provide assistance data in the form of base station locations so mobile devices may be found by trilateration.
Base stations conforming to the Long-Term Evolution (LTE) standard provide expected OTDOA measurements. The base stations are also known as Evolved Node B (e-NB) stations. OTDOA pertains to the received time difference between signals from two or more cells received at a mobile device. In LTE based positioning using OTDOA, a server may provide a mobile device with a list of potential cells to search. The UE may measure and report OTDOA for signals received from the detected cells. For further information on OTDOA signals, see U.S. Application Ser. No. 61/492,742, entitled “Hybrid positioning using LTE's OTDOA and GNSS measurements,” which was filed on Jun. 2, 2011, is assigned to the assignee hereof, and U.S. application Ser. No. 13/287,882, entitled “Hybrid positioning using synchronous and asynchronous techniques,” which was filed on Nov. 2, 2011, and is assigned to the assignee hereof.
By using the reported measurements for at least two detected e-NBs in addition to the serving e-NB, the location of the mobile device can be trilaterated. For example, the time differences may be used by the mobile device or a carrier's positioning server to derive curves that intersect at or near the mobile device to determine the position of the mobile device.
When a mobile device relies on a server for assistance data or positioning computations, these servers are carrier-provided servers in which the user's network provider may control and charge for access to its location server. Thus, the carrier maintains sole possession for providing assistance data to a mobile device. Therefore, to ensure high availability and redundancy in case of outages and for other economic reasons, there is a need for a third-party location server disassociated from, unregulated and not controlled by the network carrier.